Lower Urinary Tract Obstruction

Lower urinary tract obstruction is defined as partial or complete obstruction of the urinary tract at the level of the urethra and the bladder. The posterior urethral valves are the most common cause, 9 percent of the fetal uropathies. The incidence range is wide, because of different databases show different populations. The most severe obstructive uropathy is in patients with kidney damage, oligohydramnios and pulmonary insufficiency. If no prenatal intervention is performed, 45 percent of these patients die in the first 3 weeks of life and 25 percent have renal failure. In utero therapy is indicated to prevent renal damage and pulmonary hypoplasia in cases associated with progressive development of oligohydramnios. The treatment is usually limited to male fetuses with bladder outlet obstruction. The selection criteria (contraindications of fetal intervention) are: normal amniotic fluid volume, suggestion of nonobstructive dilatation of the urinary tract, sonographic evidence of renal cystic dysplasia, abnormal fetal urinary parameters, abnormal karyotype, presence of associated major congenital anomalies, fetal urinary parameters are above threshold. At the follow up after a prenatal intervention showed an apparent statistically significant improvement in perinatal survival with prenatal intervention relative to no intervention. Furthermore, there was no significant difference between the proportions of survivors with normal renal function who underwent bladder drainage and those who did not. Improved perinatal survival was also suggested in those fetuses with a poor prognosis. A nonsignificant improvement in perinatal survival for those fetuses with a good prognosis was also seen.